Controlled pressure platen

ABSTRACT

A controlled pressure platen is disclosed having a pair of actuating toggle linkages. A driving toggle linkage acts on a driven toggle linkage to move the platen at a controlled pressure. The driving toggle linkage has a biased resist point, the biasing of which determines the minimum pressure applied by the platen.

Unite States Patent Beachner 1 Sept. 26, 1972 [54] CONTROLLED PRESSURE PLATEN [72] Inventor: Robert W. Beachner, Rochester,

[73] Assignee: Burroughs Corporation, Detroit,

Mich.

22 Filed: Oct. 30, 1970 211 Appl. No.: 85,546

[52] U.S. Cl ..74/520, 101/297 [51] Int.Cl. ..G05g 1/04 [58] Field of Search ..74/520; 101/291, 297, 298,

l0l/30l, 302, 303, 304, 305

[56] References Cited UNITED STATES PATENTS 3,522,742 8/1970 Behrens ..74/520 Bastian ..74/5 20 Randall ..74/5 20 Primary ExaminerWi1liam F. ODea Assistant ExaminerWesley S. Ratliff, Jr. Attorney-Kenneth L. Miller and Kevin R. Peterson [5 7] ABSTRACT A controlled pressure platen is disclosed having a pair of actuating toggle linkages. A driving toggle linkage acts on a driven toggle linkage to move the platen at a controlled pressure. The driving toggle linkage has a biased resist point, the biasing of which determines the minimum pressure applied by the platen.

1 Claim, 3 Drawing Figures PATENTEDsEP2s I972 SHEET 1 OF 2 INVENTOR. ROBER T W. BE ACHNER ZMr V ATTORNEY INVENTOR.

ATTORNEY PATENTEDsms m2 sum 2 or 2 7 J 7 5 5 cw M? 3 J23 I .A f II I [IL] @Q 51. A 2% 1 3 w ROBERT W. BEACHNER CONTROLLED PRESSURE PLATEN BACKGROUND OF THE INVENTION This invention relates generally to a controlled pressure platen and more particularly to a driving linkage for a platen for use in a printing machine where the printing pressure is controlled by the platen driving linkage.

The platen of the present invention is particularly useful in a printing machine used for encoding information onto a document which is to be processed by automatic character recognition equipment. Equipment of the latter type is particularly sensitive to the quality of the print which is to be read either optically or magnetically. y

In printinginformation onto a document to be automatically processed, the amount of pressure applied has to be controlled. If too little pressure is used, not enough ink will adhere to the document. If excessive pressure is used, an excess of ink can be forced onto the document or even worse the document can be cut through by the print type. If the same thickness document is to be printed each time, the machine can be adjusted to a fixed pressure. However, if different thicknesses are to be printed in a random order, such as mixed, single, and multipart forms, a means must be provided to control the pressure used in printing. The novel platen drive of the present invention will provide a controlled printing pressure regardless of the number of sheets being printed.

SUMMARY OF THE INVENTION In accordance with the present invention, a platen is provided with a driven toggle linkage which is connected to a resist point. A second driving toggle linkage is connected to the break point of the driven toggle linkage and to a moveable resist point. When the driving toggle linkage is aligned, it causes the driven toggle linkage to align and move the platen. If a thick work piece or several sheets of paper are to be acted on by the platen, the driven toggle will encounter a resistive force which will make it difficult for the toggle to align.

. To compensate for the increase in pressure the resist point of the driving toggle will move against a baising.

means to relieve the driving force from the driven toggle. The amount of force applied by the driving toggle is determined by the strength of the biasing means and will remain relatively constant regardless of the thickness of the material acted on by the platen and driven toggle. So long as the driven toggle encounters an excessive force in attempting to line up, the biasing means will relieve the pressure applied against the driven toggle to control the pressure applied by the platen.

BRIEF DESCRIPTION OF THE DRAWINGS The invention, both as to its organization and method of operation, together with further advantages thereof, will best be understood by reference to the following detailed description taken in connection with the accompanying drawings, in which:

FIG. 1 is a partial perspective view of the platen drive and pressure control linkages shown as they would appear with the platen operating against a resistive load.

FIG. 2 is a diagramatic view of the platen control linkages when little resistance to platen movement is encountered.

FIG. 3 is a diagramatic view of the platen control linkages when a large resistive force is encountered.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1, the constant pressure platen is shown supported between the side frames 11 and 13 of a machine. The platen 15 is attached to a supporting frame 17 which is pivotally mounted on a cross shaft 19 which extends through the side frames of the machine.

A pair of spaced toggle linkages 21 and 23 are mounted between a pair of spaced lugs 25 and 27 formed on the back of the supporting member 17 and a cross shaft 29 mounted between the side frames of the machine. Depending from the break point of toggle pairs 21 and 23 are a second pair of toggle linkages 31 and 33, respectively. The toggle linkage 31 has a cam roller 35 and the toggle linkage 33 has a cam roller 37 which are in contact with cams 39 and 41, respectively, on machine drive shaft 43. The drive shaft 43 is rotated by a single revolution clutch 45.

As previously indicated, the toggle linkages 31 and 33 depend from the break point of toggles 21 and 23. The lower portion of the toggles are supported by a cross shaft 47 which passes through an aperture 49 in the side frame 11. A similar aperture is provided in the side frame 13. The cross shaft 47 is supported by a lever arm 51 which is pivoted on cross shaft 19 and is biased in an upward direction by a coil spring 53 which is attached to a lug 55 on the lever arm 51 and to a lug 57 mounted on a projection 59 which extends from the side frame of the machine. The opposite end of the cross shaft 47 is similarly supported by a lever arm and biasing coil spring not shown.

Turning now to FIG. 2, the control pressure linkage is shown as it would appear when the platen is closed against a very slight force. The links forming the upper toggle linkage 21 are lined up between the cross shaft 29 and theplaten. The links forming the toggle linkage 31 are also lined up between the break point of the toggle 21 and the cross shaft 47 which forms a floating toggle resist point. A spring 61 is provided to break the toggle 31 after the cam 39 has passed over center in driving cam roller 35. When there is only a slight amount of backward pressure, the spring 53 retains the lever arm 51 and the cross shaft 47 in an upward position.

Referring now to FIG. 3, the control pressure linkage is shown as it would appear when a substantial resistive force impeded the lining up of the upper toggle linkage 21. In this case, the toggle linkage 31 lines up between the break point of the toggle 21 and cross shaft 47. The link forming the upper toggle 21 cannot line up in view of the excessive resistive force on the platen. To compensate for this force the lower toggle resist point, cross shaft 47, moves downward in aperture 49 against the tension of coil spring 53 which is exerted through lever arm 51. The coil spring 53 exerts a control pressure in an upward direction against the toggle linkage 31 and the toggle 21 and establishes a minimum pressure for the controlled pressure platen.

The pressure exerted by the control pressure platen is at a maximum when only one or a very few sheets are present in the printing couple formed between the platen and a print wheel. As the thickness of the work piece or the number of sheets increases, the pressure on the platen is determined by the biasing means which urges lever arm 51 in an upward direction. While a coil spring 53 is shown in the drawings, it is obvious that a leaf spring, a piston, a torsion bar, a block of resilient material or any other equivalent device could be used to urge the lever arm 51 and in turn cross shaft 47 in an axial direction aligned with and opposed to the break point of the upper toggle linkage.

In the description of the preferred embodiment of the present invention the directional terms upper and lower refer to the device as shown in the several figures of the drawings. Obviously the control pressure platen can operate in a different orientation and the terms should be so construed.

While a particular embodiment of the invention has been shown, it will be understood, of course, that it is not desired that the invention be limited thereto since modifications may be made, and it is, therefore, contemplated by the appended claims to cover any such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

l. A controlled pressure platen for use in an encoding apparatus for encoding information on items to be read by means of automatic character recognition equipment comprising;

a platen rockable toward and away from a backup anvil with which said platen is associated adapted to receive a document for printing thereon,

a pair of driving toggle linkages,

a pair of driven toggle linkages,

the driving toggle linkages depending from the break point of said driven toggle linkages,

said driving toggle linkages being fixed to and pivotally movable with a cross shaft extending therebetween,

said cross shaft being capable of slight vertical shifting movement effective to accommodate varying degrees of platen pressure,

tension spring means biasing said cross shaft in a direction to resist movement of said toggle linkages effective to control said platen pressure,

a drive shaft rotated by a single revolution clutch,

and

cam means on said drive shaft operably associated with both of said driving toggle linkages and said drive shaft to cause said linkages to reciprocate said platen toward and away from an item to effect printing thereon in response to rotative driving action of said cam means. 

1. A controlled pressure platen for use in an encoding apparatus for encoding information on items to be read by means of automatic character recognition equipment comprising; a platen rockable toward and away from a backup anvil with which said platen is associated adapted to receive a document for printing thereon, a pair of driving toggle linkages, a pair of driven toggle linkages, the driving toggle linkages depending from the break point of said driven toggle linkages, said driving toggle linkages being fixed to and pivotally movable with a cross shaft extending therebetween, said cross shaft being capable of slight vertical shifting movement effective to accommodate varying degrees of platen pressure, tension spring means biasing said cross shaft in a direction to resist movement of said toggle linkages effective to control said platen pressure, a drive shaft rotated by a single revolution clutch, and cam means on said drive shaft operably associated with both of said driving toggle linkages and said drive shaft to cause said linkages to reciprocate said platen toward and away from an item to effect printing thereon in response to rotative driving action of said cam means. 